The present invention relates generally to filtration apparatus and, in a preferred embodiment thereof, more particularly provides structurally reinforced, self-aligning panel filter apparatus with associated clamping, face sealing and backflushing structure, the filter apparatus being positionable to extend across a discharge opening formed in a wall separating the material collecting and clean air flow chamber portions of a particulate collecting system.
The mechanical forces generated by industrial and other processes are often imparted to associated micron size material to make them airborne, thereby creating, via the resulting dust, undesirable hygienic and environmental conditions. In the interest of controlling these conditions, several types of particulate collecting systems utilizing an air flow stream have been devised to scavenge dust and other airborne particulates into chambered receivers having a material collecting chamber with an air flow stream inlet and outlet. Such collecting systems commonly include means for filtering particles from the flow stream traversing the material collecting chamber prior to its discharge therefrom. In the typical particulate collecting system, the interior of the material collecting chamber is separated from a clean air flow discharge chamber by a dividing wall having a discharge opening therein in which the filter means are operatively disposed to collect particulate matter and prevent it from being discharged into the clean air flow chamber.
A variety of chambered material receivers are present in today's market. Examples of such apparatus are disclosed in U.S. Pat. Nos. 4,272,262; 4,331,459; and 4,661,131. The particulate collection apparatus disclosed in these patents utilize panel filters which bar particulates from being discharged from the collecting chamber outlets. The filters are periodically cleaned by backflushing systems which utilize sudden reverse flows of high energy gas directed by reverse flow passages which are a permanent part of the material receiver and/or the filter apparatus. In other words, in these conventional particulate collection structures, the reverse flow cleaning passages are constructed to be a permanent part of the particulate collection system housing and/or a permanent part of the filter structure itself.
Further, the filters of these conventional systems are arranged to clean the air flow stream as it is discharged from the material collecting chamber. Accordingly, the filters are mounted in arrangements facilitating particulate removal upstream from the collecting chamber outlet. Means mounted downstream from this outlet provide for reverse flow filter cleaning as previously described. To service the filters in these conventional systems, it is typically necessary to enter the "dirty" side of the apparatus--i.e., the interior of the material collection chamber. The backflushing systems for the filter element or elements are positioned in the aforementioned clean air discharge chamber downstream from the material collecting chamber, and servicing of the backflushing system typically entails entry into this downstream chamber. Thus, both chambers of the particulate collecting system must be entered for servicing its components.
U.S. Pat. No. 4,740,221 provides a self-cleaning filter system incorporating a filter mounted to a clean air flow conductor. After interconnecting the filter and its associated flow conductor, the resulting assembly is installed in the material collecting chamber via the clean air discharge chamber and is secured to the downstream side of the material collecting chamber flow stream outlet. The flow conductor, when operatively engaged with the discharge outlet, provides means for aligning and sealing the filter. In other words, the filter is dependent upon the flow conductor for structural integrity to permit the assembly to be inserted into the material collecting chamber through its air outlet. Thus, the filter and its associated flow conductor must be pre-assembled before installing them through the chamber outlet.
The previously referenced U.S. Pat. Nos. 4,331,459 and 4,661,131 disclose air filtering systems incorporating panel or planar air filter structures in unitized construction with clean air flow conductors. The unitized filter/flow conductor unit is installed by entry into the material collecting chamber (i.e., the "dirty" side of the material collection system) and through clamping engagement over the material collecting chamber air outlet. Since the flow tube is a unitary part of the filter structure, the flow tube must be thrown away when its associated filter portion needs to be replaced. The previously referenced U.S. Pat. No. 4,272,262 discloses panel filters mounted to a relatively large flow tube structure permanently incorporated in the material collecting chamber. The filter is installed through entry to this chamber. The large, permanently mounted flow conductor structure undesirably consumes a considerable portion of the material receiving chamber.
In other instances, as exemplified in U.S. Pat. Nos. 4,345,353 and 4,328,014, a panel filter is engaged to the downstream face surrounding the air/material receiver outlet. The filter is aligned to the outlet opening by virtue of the alignment of a filter clamping device to the opening and by alignment of the filter with its clamping device. In other words, the filter is mated to its clamping device and the clamping device is mated to the receiver downstream air outlet.
Conventional particulate collecting systems such as those disclosed in the previously referenced U.S. Pat. Nos. 4,258,451; 4,328,014; and 4,272,262 typically provide filter structures having relatively light weight filtration media. Commonly, to facilitate fabrication, the frames of these filter structures are also of relatively light weight material. The frame work must retain the filter media and seal integrity against the stress of air flow and filter cleaning backflushing. Typically, the filter structure forces resulting from air flow pressure loss across dirty filter medial can become quite high. For instance, a four square foot panel filter having a pressure drop of eight inches of water will be subjected to a lateral thrust of approximately 170 pounds. Field experience has presented many cases of seal leakage in panel filters. Obviously, structural integrity of both the filter frame and its clamping means are suspect in these cases.
The well-known problems, disadvantages and limitations associated with the filter structures and associated backflushing structures of the above-mentioned and other conventional particulate collection systems may be summarized as follows:
1. Filter reverse flow cleaning passages in many instances are integral and permanent parts of the system housing or the filter structure;
2. For most conventional systems, filter servicing requires entry into the system material receiving chambers (i.e., the "dirty" sides of the systems);
3. In at least one instance, to eliminate the need for entering the system's material receiving chamber for filter service, the filter must be attached to the flow conductor prior to assembly through the chamber outlet;
4. Unitized construction of the panel filter and its associated air flow conductor requires that both be discarded at the time of filter replacement;
5. Clean air flow conductors for certain panel filters are relatively large and extend into the material receiving chamber, thereby undesirably consuming considerable chamber space;
6. Panel filters sealed to downstream faces of chamber air discharge outlets are typically dependent upon their associated clamping structure to align them to the material receiving chamber outlet; and
7. Panel type filters are typically constructed using light structural framework that essentially precludes the rigid clamping of the filter structure necessary to overcome high thrust loads caused by air pressure drop across the filter.
In view of the foregoing, it is an object of the present invention to provide improved panel filter and associated backflushing apparatus which eliminates or minimizes the above-mentioned and other problems, disadvantages and limitations typically associated with the filter and backflushing structures in conventional particulate collection systems.